The Age Effect: How Your Fertility Changes as You Get Older


6 min read

We know fertility challenges associated with age can exacerbate what is already a stressful situation. We believe the more facts you have, the more in control you can be of your body and your future. Our goal with this article is to provide valuable information regarding age and fertility that can help you with your family and fertility planning.

The Basics of the Biological clock

It's common to hear the phrase “ my biological clock is ticking” in reference to the pressure to start a family before your body has aged out of that possibility. The idea of a biological clock stems from the fact that the human body is designed to have a small window of time optimal for reproducing.   

The principle of a biological clock applies to both those assigned female and those assigned male at birth. For those assigned female, the onset of the decline in fertility can vary, but as you approach menopause, the body will run out of eggs and no longer be able to conceive a pregnancy naturally. 

For those assigned male, there’s still some sort of biological clock-type urge to reproduce, but the window of time may not be as tight. Whereas ovaries have a fixed number of eggs from birth, males constantly produce new sperm throughout their life, so there isn’t the same amount of pressure to have kids before time runs out. 

No matter your sex, some aspects of your fertility decline with age and can affect your family planning goals. 

Aging and Female Fertility

Females are born with all of the eggs that they will ever have. In fact, the egg number begins to decline even before a female infant is born! The most fertile time tends to be in your early to mid 20s. From around the age of 35, the decline in fertility tends to begin to steepen and becomes the most rapid by the age of 40 through menopause.

There are a few ways to measure and track your fertility. The most typical values used to assess fertility status are AMH (Anti-Mullerian Hormone), FSH (Follicle Stimulating Hormone), and AFC (Antral Follicle Count).

  • AMH is a hormone released by the cells that surround each immature egg in the ovaries. Based on the quantity of this hormone in the bloodstream, a fertility specialist can estimate the amount of eggs remaining in the ovaries, which is known as your Ovarian Reserve. The AMH value is typically at its highest in your early to mid 20s and decreases as you get older and especially as you reach 40 and begin menopause.

  • FSH is a hormone produced by the pituitary gland. It’s responsible for causing a Follicle in the ovaries to grow and develop a mature egg to ovulate each cycle. When there are fewer eggs in the ovaries, the body releases more and more FSH to try to get the ovaries to respond and grow a follicle. The higher the level of FSH, the harder the body is working to continue to ovulate. Consistently high FSH levels often indicate the beginning of menopause.

  • AFC is the number of tiny immature follicles, known as antral follicles, visible by ultrasound at the beginning of the menstrual cycle, typically on cycle day 2 or 3. Each month, your body selects a small group of these antral follicles and the size of the group can also shed light on your ovarian reserve. The fewer eggs remaining in the ovaries, the fewer antral follicles will be visible each month. Therefore, the AFC is also one of the factors used to help estimate ovarian reserve.

Not only does the number of eggs in the ovaries begin to decrease with age, but the quality of the remaining eggs also tends to decline. The decrease in quality tends to lead to an increased risk of genetic anomalies, like Down Syndrome. The lower quality eggs that are ovulated as you reach your late 30s and early 40s are often the cause of the increased miscarriage rate associated with aging. 

In recent years, many people are pushing off starting a family. Want more information about planning a family in your 30s? Check out our article, Fertility Planning: Everything to Know at 30.

Aging and Male Fertility

Often when it comes to fertility, the pressure of aging falls heavily on females. For a long time, the thought was that as females age their fertility declines, but male fertility remains consistent throughout their life. Although males continue to produce sperm throughout their lives, recent research has come to suggest there’s a natural decline in sperm quality and quantity with age. The decrease in quality affects the genetic material within the sperm that would go on to fertilize an egg as well as the sperm’s shape and ability to swim. 

Studies have shown associations with older fathers and an increased likelihood of having a child born with autism or schizophrenia. There’s no conclusive evidence on a specific age associated with the start of these increased risks, but most evidence suggests that males carry increased risk when having children beyond their mid 40s. 

Studies have also shown that the age of the father can contribute to a longer time trying to conceive as well as an increased risk of miscarriages. Like eggs in the ovaries, this is likely due to the fact that the DNA in the sperm of older males is more prone to contain errors or structural abnormalities that are not compatible with a successful fertilization, implantation, and growth of an embryo. 

No matter your sex assigned at birth, as you age, fertility naturally declines. This can make trying to conceive harder and take a longer time. The ticking of the biological clock is why there are age-based recommendations for when to see a fertility specialist when trying to conceive.

When to Seek Help From A Fertility Specialist

As you age, the recommended time for trying to conceive before seeking an evaluation from a fertility specialist becomes shorter. For females younger than 35, it’s recommended to try to conceive for 1 year without success before seeing a doctor. On the other hand, if you’re 40 years old or older, it’s recommended to see a fertility specialist as soon as you start trying to get pregnant. The reason for the prompt medical assessment is that fertility begins to rapidly decline at this time so it’s best to waste as little time as possible in case assistance is necessary to try to conceive. 

Recommended time trying to conceive before seeking help from a fertility specialist by age of egg provider

When you create a plan for fertility and family building goals, be sure to consider age and its effect on fertility. If you're armed with knowledge about these effects, you'll be a better advocate for yourself.


DeWeerdt, Sarah. 2017. “The Link between Autism and Older Parents Is Clear, but the Why Is Not.” Washington Post, December 16, 2017, sec. Health & Science.

Kluiver, Hilde de, Jacobine E. Buizer‐Voskamp, Conor V. Dolan, and Dorret I. Boomsma. 2017. “Paternal Age and Psychiatric Disorders: A Review.” American Journal of Medical Genetics 174 (3): 202–13.